I'm kind of surprised that nobody appears to have asked this before -- my search in the forums came up empty.

With PDF in particular, I think it is not uncommon that it would be desirable to have multiple instances managed with a single book entry (e.g., an original PDF and one post-processed for small-screen devices). However, due to the way Calibre automatically replaces existing files of a given format when a new one in the same format is added, I'm left wishing for something which does not appear to be possible.

Is there a way to keep multiple files of the same format with a single book entry? If not by design, is there a workaround other than adding differently-named files manually to the book's directory?